1. Field of the Invention
The present invention relates to a radiotherapy apparatus and a radiation irradiating method, and especially relates to a radiotherapy apparatus and a radiation irradiating method in which a high stability of doses can be realized in radiotherapy for, for example, a prostate and a lung as an affected region of tumor in a body's interior.
2. Description of Related Art
A radiotherapy apparatus for treating a patient by irradiating a therapeutic radiation to an affected region (a tumor) is widely known. The radiotherapy is required to have a high therapeutic effect. Additionally, it is required to irradiate only a predetermined dose of the therapeutic radiation to the affected region more accurately, and fluctuation of the dose is required to be small.
U.S. Pat. No. 4,427,890 discloses a method for controlling energy of an electron beam by monitoring an electric current in a target which converts an electron beam into the X-ray. US Patent Application Publication No. 2007/0248214 discloses a method for controlling energy of an electron beam by measuring a dose distribution of the X-ray with using a transmission type dosimeter having a dispersion type terminal electrode and by controlling power so as to correct a change of the dose distribution of the X-ray.